Lift device attachment for motorboats



Jan. 1o, 1961 K. N. UNGER 2,967,503

LIFT DEVICE ATTACHMENT FOR MOTORBOATS Filed Aug. 18, 1958 2 Sheets-Sheet 1 Jan. 10, 1961 K. N. UNGER 2,967,503

LIFT DEVICE ATTACHMENT FOR MOTORBOATS Filed Aug. 18, 1958 2 Sheets-Sheet 2 lHlllllll Ill!!! Y United States Patent() F Lnrr DEVICE ATTACHMENT FOR MoroRBoATs Kenneth N. Unger, Chicago, Ill. (195 Olmsted Road, Riverside, Ill.)

Filed Aug. 18, 1958, Ser. No. 755,570

3 Claims. (Cl. 114-665) This invention relates to a device for attachment to the keel of a motorboat for providing -a lifting force to the motorboat as it advances forwardly through a body of water.

The structure of the present invention is intended for use on small motor boats of the type commonly used on inland lakes and rivers. When it is attached to the keel of a forwardly moving boat, lift is created which raises the hull upwardly toward the water surface and reduces drag caused by the friction of the water against the hull. The structural arrangement of the invention prevents access of the atmosphere to the upper or low pressure face of the lift device. This :assures maximum lift by combining the force created by movement of the lifting surface through water with the upward force caused by the decreased pressure just above the inclined upper face of the device. Furthermore, even though a boat using the device merely skims the surface of the water during movement, the formation of the lift surface and its stabilizing tin maintain remarkably good stability and render the boat highly maneuverable at all times.

The primary object of the invention is to provide a new and improved lift device for attachment to the keels of motorboats to impart lifting forces in order to increase the operating efficiency and velocity of a motorboat during forward movement through a body of water.

Another object is to provide such a device which is adapted for attachment to any one of a number of types of motorboat keels currently in use, and which can readily be attached in operative position by the ordinary boat user.

A further object is to provide a lift device having a planar, pointed attacking portion mounted on a depending stabilizer iin, the attacking portion being upwardly inclined in a forward direction to impart lift to the motorboat.

Still another object is to provide a lift device which includes a pointed attacking portion adjustablyV mounted on a depending n so that the angle of attack of the lifting portion can be varied to give maximum lifting and operating efciency with various types of motorboats.

Yet another object is to provide a lift device for attachment to motorboats in which the lift surface is triangular and pointed in the `direction of forward motion of the motorboat, the trailing edges of the wedge-shaped surface being symmetrically disposed about a thin flat stabilizer fin so that the lift surface and the lin cooperatively impart stability to the boat at increased velocities.

The invention is illustrated in a prefer-red embodiment in the accompanying drawings, in which:

Fig. 1 is a side elevational view of the lift device shown mounted in preferred operative position on a line through the center of gravity of a boat and its motor, the upper dotted line illustrating the approximate position of the boat at rest in the water and the lower dotted line illustrating the preferred position of the boat when in motion in the water under the lifting inuence of the device;

Fig. 2 is a top plan view of the lift device detached from the motor boat;

2,967,503 Patented an. Y 10, A1961 ICC Fig. 3 is a side elevational view of the lift device of Fig. 2;

F Fig. 4 is a fragmentary plan view of the underside of Fig. 5 is a fragmentary sectional view illustrating the manner of attachment of the lift device to a boat having a block-type keel;

Fig. 6 is a fragmentary sectional view illustrating the manner of attachment of the lift device to a boat having arib-type keel; and

Fig. 7 is a fragmentary sectional view illustrating the manner of attchment of the lift device to a boat having a wooden keel.

In the embodiment illustrated, a conventional boat 10 is provided with the usual motor 11, and the lift device of the present invention, generally designated 12, is shown mounted on a vertical line through the center of gravity of the boat and its motor.

The lift device 12, preferably formed of structural.

aluminum, may be provided with a thin, flat supporting strut or stabilizer lin 13 having 1a flanged upper edge 14 which has a number of apertures 15 each for receiving the shank of a bolt 16 (shown in Figs. 5 and 6) or the shank of a screw 17 (shown in Fig. 7). In Fig. 5, a block-type keel 18 of a plastic or molded plywood boat is illustrated. The bolts 16 extend through the apertures 15 of the upper edge 14 `and through the block keel 18 on the booton of the boat. Rubber or neoprene washers 20 secure the shanks of the bolts 16 and nuts 21 are thread upon the free ends of the bolts 16 to lirmly attach the fin 13 to the block keel 18 in watertight relation.

In Fig. 6 a rib-type keel 22 of an aluminum boat is illustrated. The same bolts 16, washers 20 and nuts 21 are utilized to attach the fin 13 to the rib keel 22. In addition, elangated adaptor blocks 23 are apertured at 24 and shaped to closely fit against the longitudinally extending sides of the rib keel 22. The bolts 16 are then passed upwardly through the apertures in the adaptor blocks 23 to secure the lin 13 in place in a manner similar to that described above.

In Fig. 7, a wooden keel 25 of a wood strip boat is shown. The iin 13 is attached by merely advancing a number of screws upwardly through the apertures 15 of vthe upper edge 14 and into the wooden keel 25.

Referring to Figs. 2 and 3, the stabilizer lin 13 has a thin depending portion 19 which is preferably generally rounded at its periphery, the smallest radius of curvature being located in its forward portion 26 and with the radii -of curvatures being gradually increased in a direction toward its rear portion 27. The shape and size of the depending iin may be altered with the particular boat to lend the proper stabilizing inlluence. The central part'of the depending portion 19 has a pair of opposed brackets 28 and 30 mounted on its opposite sides by machine -screws 31. Each of the brackets 28 and 30 and the lin V1'3 are lappropriately apertured to receive a journal bar 32 which is held in place by adjustable screws 33, and forms outwardly extending trunnions. The trunnions or journal bar 32 is positioned perpendicular to the opposite surfaces of the iin 13.

The lift device 12 is provided with a lift plate 35 preferably formed also from structural aluminum. The lift plate may be formed in the shape of an isosceles triangle, which provides remarkable stability to the boat, so that it has a forward attacking portion 36 and a pair of rearward trailing portions 37 and 38 which are symmetrically disposed on opposite sides of the stabilizer lin 13.

The lift plate 35 is preferably swingably mounted upon the depending portion 19 of the stabilizer fin 13 and cooperates therewith to enhance stability during movement. As best seen in Fig. 4, the Ilift plate 35 is provided in its central portion with a longitudinally extending elongated slot 40 which is of a size to closely receive the free end of the depending portion 19. The upper face of the lift plate 3'5 may be provided with a pair' of bearing brackets 41 and 42 which are conventionally secured in place by machine screws 43. Each of the brackets has a pair of rearwardly extending tangs 44, 45, 46 and 47 which are apertured to rotatably receive the opposite ends of the trunnions 32. It can be readily seen from Figs. 3 and 4 that suicient clearances are maintained between the depending portion 19 and opposite ends of the slot 40 so that the position of the lift plate 35 may be varied in relation to the depending portion 19.

In order to adapt the lift device 12 to boats of varying sizes, lengths and weights, the device is preferably provided with means for adjusting the angle of attack (e.g. between 2 and 12 of inclination) of the lift plate 35 when in operative position. As best seen in Fig. 3, means are provided for raising or lowering the forward attacking portion 36 so that optimum operating conditions may be realized when the lift device is used with a particular type of boat. A fastener bracket 48 is iixedly secured to the forward attacking portion 36 by a number of machine screws 50. The bracket 48 also has a pair of apertured tangs 51 which are laterally spaced to straddle the forward portion 26 of the stabilizer iin 13. The iin 13 is in turn provided with a number of apertures 52 which may be selectively alined with the apertured tangs 51 by swinging the lift plate 35 upon the trunnions 32. When the desired apertures are brought into alinement, a fastener pin 53 may be inserted to maintain the lift plate at the desired degree of angular elevation. Conventional means may be employed to retain the pin 53 in place during operation of the device.

When using the lift device 12, the boat operator first determines the balance point of the boat with its motor which is approximately on -a vertical line through the center of gravity. The lift device is mounted directly beneath the center of gravity and its trailing portions 37 and 38 are precisely positioned symmetrically of the keel with the forward attacking portion 36 directed toward the bow of the boat. The lift plate 35 may then be adjusted by trial and error to the proper inclination for the particular boat being used. Of course, additional increments of adjustment may be provided if desired without departing from the scope of the invention.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom for some modifications will be obvious to those skilled in the art.

I claim:

l. A device for attachment to the bottom of a motorboat to impart lift during movement through water, comprising: a ilat, thin stabilizer iin having an upper edge adapted for attachment in operative position to the keel of a motorboat, said tin having a generally peripherally rounded depending portion extending downwardly when in operative position, the depending portion being provided with centrally disposed trunnions extending perpendicularly outwardly of its opposite sides; a flat, triangular lift plate having a pointed forward attacking portion and similar rearward trailing portions, said lift plate having a central slot of a size to receive the free end of said depending portion, said slot being positioned so that the trailing portions are symmetrically disposed on opposite sides of said depending portion, the lift plate being provided with laterally spaced bearings on opposite sides of the slot to receive said trunnions and swingably mount said lift plate; and adjustable fastening means positioned on said forward attacking portion for adjustably securing the forward attacking portion to the depending portion to vary the angle of attack of the lift plate when in operative position.

2. A device for attachment to the bottom of a motorboat to impart uniform lift to the entire motorboat during its forward motion in water, comprising: a thin supporting tin provided with a top edge adapted for attachment in operative position to the keel of the motorboat, said fin having a depending stabilizing portion extending downwardly into the water when the device is in operative position; an integral at lift plate having a forward attacking portion and diverging trailing portions extending in a rearward direction and being symmetrically disposed on opposite sides of the supporting stabilizer lin, said lift plate being pivotally secured to the medial portion of said fin between said top edge and the free end of said depending portion for swinging movement parallel to the plane of the n; and cooperating fastening means on the tin and the lift plate for securing the lift plate against said swinging movement to position said lift plate at a forwardly inclined angle whereby said n and said lift plate mutually cooperate during forward motion of the motorboat to impart lift to the motorboat toward the surface of the water while retaining stability and maneuverability thereof during operation.

3. In combination, a motorboat having a keel, and a lift device for attachment to said keel beneath the center of gravity of the motorboat to impart uniform lift thereto during its forward motion in water, the lift device comprising, a supporting lin provided with a top edge adapted for attachment in operative position to the keel of the motorboat, said fin having a depending stabilizer portion extending downwardly into the water when the device is in operative position, an integral at lift plate having a forward attacking portion and diverging trailing portions extending in a rearward direction and being symmetrically disposed on opposite sides of the supporting stabilizer iin, said lift plate being swingably secured to said n beneath the center of gravity of the motorboat for movement parallel to the plane of the iin; and cooperating fastening means on the fin and the lift plate for securing the lift plate against swinging movement, said fastening means being selectively engageable so as to vary the inclined angle of the forward attacking portion with respect to the horizontal, whereby said lift plate and said tin mutually cooperate to impart lift to the entire motorboat toward the surface of the water while retaining stability and maneuverability thereof during operation.

References Cited in the tile of this patent UNITED STATES PATENTS 874,031 Palmer Dec. 17, 1907 1,911,192 Harvey May 30, 1933 1,923,958 Wesnigk Aug. 22, 1933 2,550,220 Bussei Apr. 24, 1951 2,689,540 Kasey Sept. 21, 1954 2,751,612 Shepard June 26, 1956 2,832,304 Elyosius et al Apr. 29, 1958 2,858,788 Lyman Nov. 4, 1958 FOREIGN PATENTS 264,809 Switzerland Feb. 1, 1950 

